Is CT bulletproof? On the use of CT for characterization of bullets in forensic radiology

Abstract

PurposeForensic investigations could benefit from non-invasive in situ characterization of bullets. Therefore, the use of CT imaging was explored for the analysis of bullet geometry and composition. Bullet visualization with CT is challenging as the metal constituents suffer from excessive X-ray attenuation due to their high atomic number, density, and geometry.MethodsA metal reference phantom was developed containing small discs of various common metals (aluminum, iron, stainless steel, copper, brass, tungsten, and lead). CT images were acquired with 70–150 kVp and 200–400 mAs and were reconstructed using an extended Hounsfield unit (HU) scale (− 10,240 to + 30,710). For each material, the mean CT number (HU) was measured to construct a metal database. Different bullets (n = 11) were scanned in a soft tissue-mimicking phantom. Bullet size and shape were measured, and composition was evaluated by comparison with the metal database. Also, the effect of bullet orientation within the CT scanner was evaluated.ResultsIn the reference phantom, metals were classified into three groups according to their atomic number (Z): low (Z ≤ 13; HU < 3000), medium (Z = 25–30; HU = 13,000–20,000), and high (Z ≥ 74; HU > 30,000). External bullet contours could be accurately delineated. Internal interfaces between jacket and core could not be identified. Cross-sectional spatial profile plots of the CT number along bullets’ short axis revealed beam hardening and photon starvation effects that depended on bullet size, shape, and orientation within the CT scanner. Therefore, the CT numbers of bullets were unreliable and could not be used for material characterization by comparison with the reference phantom.ConclusionCT-based characterization of bullets was feasible in terms of size and shape but not composition.

Reduction of CT Artifacts Using Polyetheretherketone (PEEK), Polyetherketoneketone (PEKK), Polyphenylsulfone (PPSU), and Polyethylene (PE) Reconstruction Plates in Oral Oncology

“…In these cases, primary reconstruction of the mandible is usually conducted by implantation of a patient-specific titanium reconstruction plate with or without bone graft (4). Titanium offers a high degree of mechanical stability and biocompatibility, however, entails the disadvantage of causing metal streak and blooming artifacts in computer-tomography (CT) images due to its high atomic number (5)(6)(7). The density of human tissues can generally be represented as Hounsfield Unit (HU) values between -1024 and +3071 on a 12-bit conventional Hounsfield-Unit scale (CHU) (8).…”

Extended Computed Tomography Scale Images Provide a Detailed Assessment of Metal Screws and Are Superior to Standard Computed Tomography Scale Images and Digital Radiography at Detecting Experimentally Induced Screw Fractures In Vitro

“…Reports of similar applications of ECTS are scarce and limited to forensic medicine. 13 18 Other clinical applications of ECTS in veterinary medicine, such as for diagnosing failure in other types of implants, smaller screws, or for assessing implant positioning following complex surgical procedures (e.g., spinal stabilization), warrant further investigation.…”

The Outcome of the Forensic Triage Preceding Disaster Victim Identification in the Downing of Malaysia Airlines Flight 17

“…To minimise artefacts and improve material characterisation, dual-energy CT may be used [ 12–14 ]. However, this method cannot normally be used to determine the composition of materials and objects [ 15 ]. Because most foreign objects encountered in a forensic investigation (e.g.…”

“…Industrial scanners may use energies up to 320 kVp [ 16 ], but these scanners require the body to be rotated, which makes them unsuitable for PMCT. Moreover, higher X-ray energies may also affect or hamper autopsy findings [ 15 ]. In Hilversum, a mobile 16-slice clinical scanner operating at a fixed tube voltage of 120 kVp was used.…”